Storage tanks used to store industrial oils and other fluids (e.g., liquids and gasses) must be properly sealed to prevent leakage of vapors contained within the tanks. The fluids can contain volatile compounds such as hydro carbons or other contaminants which, if released, can harm the environment or persons handling the tanks. Companies can face government penalties if their storage tanks are not sufficiently vapor tight. For example, the EPA conducts leakage tests on industrial storage tanks using sophisticated infrared cameras and has the authority to levy steep penalties—even for minimal leakage that would be imperceptible without the use of such equipment.
Storage tanks are usually accessed by way of a hatch commonly known as a “thief hatch.” The base of the hatch is affixed to the body of the storage tank and includes an opening providing access to the contents of the tank. The hatch is closed using a cover, which typically produces a seal by means of a rubber gasket that compresses against the base. However, hatches typically used with fluid storage tanks are difficult to keep adequately sealed and are a common source of tank leaks. The reason is that the point of contact between the gasket and the base is at a rim of the base surrounding the base's opening, which rim has a tendency to become worn or pitted over time and use. Due to the rim's wear and tear, the gasket may fail to engage evenly against the base. Gaps caused by the uneven compression will allow vapors to escape.
Unlike a rubber gasket, which is easily replaced if it wears out, the base itself can be very costly and time consuming to remediate, given that it is intended to be permanently affixed to the storage tank. In addition, the more time it takes to remediate the hatch, the worse the problem can become, because exposure to the air can quicken the rate of corrosion.
In many cases in which a hatch fails to seal due to a worn rim, the entire hatch base will need to be decoupled from the body of the tank and replaced at great expense and effort. Replacing the base can be hazardous as well, as personnel conducting the repair may be exposed to the harmful vapors released from the storage tank during the remediation process. Often, the entire storage tank must be discarded because of the faulty hatch.